(We're no longer building the prebuilt -OSNM images; they're quick to
dynamically build; and realistically no one uses a split networkmanager
configuration anymore; and we have no incentive to provide one.)

(It happens that we started homing all the images at emulab.net as we
made the transition to Ubuntu 16 (Mitaka), so the old URN hack for
utah.cloudlab.us is only necessary for the pre-Mitaka, pre-Ubuntu16
images. All those images are unsupported and require an experiment
firewall to use in this profile, anyway.)